Vitamin D has gained increasing attention in recent years due to its impact on various physiological functions throughout the body.
What is Vitamin D?
Vitamin D is a fat-soluble vitamin. The form synthesized in the body and provided by animal-based foods is vitamin D3 (also known as cholecalciferol), while the form provided by plant-based foods is vitamin D2 (also known as ergocalciferol).
In general, the primary source of vitamin D in the human body is through a chemical reaction in the deeper layers of the skin, triggered by exposure to sunlight, especially UVB radiation. Just 10 to 30 minutes of sunlight exposure a day is sufficient to synthesize an adequate amount of vitamin D3. If sunlight exposure is inadequate, vitamin D can also be obtained through dietary intake.
However, whether obtained through diet or skin synthesis, vitamin D needs to undergo conversion in the liver and kidneys to become physiologically active before it can be utilized. Activated vitamin D plays a significant role in the metabolism and balance of calcium in the body. Early observations showed that vitamin D deficiency leads to insufficient calcium deposition in growing bones of children, resulting in decreased bone density and increased susceptibility to deformities such as rickets.
💡Currently, both the United States and the European Union recommend maintaining a serum 25-hydroxyvitamin D concentration of 50 nmol/L (or 20 ng/mL) as a target to ensure adult bone health and minimize the risk of fractures [2][3][4][5].
What are the recommended proven benefits of Vitamin D?
1. Treatment of Rickets and Osteomalacia
As early as 1824, it was discovered that consuming cod liver oil could effectively treat rickets, but the active component responsible was not identified at that time. It wasn’t until 1922 that scientist Elmer McCollum confirmed it was vitamin D in cod liver oil. Nowadays, medical institutions use vitamin D as a method for preventing and treating rickets and osteomalacia [6] [7].
2. Combining with Calcium to Prevent Osteoporosis
A meta-analysis of 53 clinical trials involving 91,791 participants found that supplementation with both vitamin D and calcium can prevent hip fractures and fractures of any type, whereas supplementation with vitamin D alone does not prevent fractures [8].
3. Combatting Various Diseases
Vitamin D may reduce the risk of cancer, multiple sclerosis, atopic dermatitis, type 1 and type 2 diabetes, the likelihood of heart disease, and the risk of contracting the flu, among other benefits. It helps improve health across different age groups[9] [10] [11] [12] [13].
4. Potential to Alleviate Depression
Vitamin D might play an essential role in regulating mood and preventing depression. Research suggests that taking vitamin D supplements can improve symptoms in individuals with depression. Additionally, studies involving fibromyalgia patients have found a common deficiency of vitamin D among those with anxiety and depression symptoms [14] [15].
5. Potential to Facilitate Weight Loss
Research has indicated that additional supplementation of calcium combined with vitamin D has appetite-suppressing effects. In another study, individuals who took daily calcium and vitamin D supplements experienced greater weight loss compared to a control group that took a placebo[16] [17] [18].
Does Vitamin D have side effects?
Long-term consumption of high doses of vitamin D exceeding 4000 IU (100 micrograms) in adults is considered unsafe and may lead to excessive levels of calcium in the blood. Side effects can include weakness, fatigue, drowsiness, headaches, loss of appetite, dry mouth, metallic taste, nausea, vomiting, and other symptoms. If high-dose vitamin D is used for short-term treatment of vitamin D deficiency, it should be done under medical supervision to avoid self-administration [19] [20] [21] [22]. For oral intake of vitamin D, the US Dietary Reference Intake recommends the following daily doses:
Infants under 1 year old: 400 IU (10 micrograms)
Ages 1-70: 600 IU (15 micrograms)
Ages 71 and older: 800 IU (20 micrograms)
These doses are considered safe and sufficient to meet the needs of 97.5% of healthy individuals.
